A fluid flow amount control valve, in which a circular curved surface of a housing is arranged at the outer periphery of a rotary valve, has been proposed. For example, refer to JP4-078874 B.
For example, the fluid flow amount control valve described in JP4-078874 B is used as a tumble flow control valve (TCV), which is configured to localize intake air flow at one side in an intake passage communicated with a combustion chamber of an internal combustion engine to generate a vertical-direction intake-air vortex flow in the combustion chamber of the internal combustion engine. In this case, if a clearance formed between an inner peripheral surface of the circular curved surface of the housing and an outer peripheral surface of a circular valve element of the rotary valve is large, the amount of leakage air may become large in a fully-closed state of the rotary valve. The intake air is leaked from the entire periphery of the circular valve element of the rotary valve. Thus, by localizing the intake air required to the TCV at one side in the intake passage, a function to generate a straight flow (localized flow) that is localized at an upper side of an intake port of the internal combustion engine in a height direction thereof may be decreased.
In order to generate a strong tumble flow in a cylinder (combustion chamber) of the internal combustion engine by generating the straight flow (localized flow) that is localized at the upper side of the intake port of the internal combustion engine, Japanese Patent Application No. 2009-092280 (filed on Apr. 6, 2009), which corresponds to U.S. patent application Ser. No. 12/754,806, has been already applied.
As shown in FIGS. 17A to 18B, a valve unit (air flow control valve) of the above-described application includes a housing 101 configured to be connected to the intake port of the internal combustion engine, a duct 102 that is inserted in and supported by the housing 101, a cover 103 that fixes an upper-side end portion of the duct 102 to an upper-side end surface of the housing 101 and covers the upper-side end portion of the duct 102, a valve shaft 104 that is rotatably supported by the housing 101, and a substantially U-shaped rotary valve (swing-type rotary valve) that reciprocates around the valve shaft 104 in a rotational direction.
The rotary valve includes a pair of connecting portions 105 that is connected to the valve shaft 104, a pair of side plates 106 that extends outward in a radial direction of the valve shaft 104 from both connecting portions 105, a valve plate 107 configured to change opening areas of air flow passages 111, 112 by being reciprocated around the valve shaft 104 in the rotational direction so as to move along a downstream end surface (circular curved line portion) of the duct 2 and the like.
Each of the side plates 106 is arranged to be opposed to an outer surface of the duct 102 with a clearance interposed therebetween.
In a fully-closed state of the rotary valve, the valve plate 107 is arranged to be opposed to the downstream end surface of the duct 102 and an air outlet of the air flow passage 111 with a clearance interposed therebetween. Furthermore, the air flow passage 111 has an opening 114 configured to generate the straight flow (localized flow) that is localized at the upper side of the intake port of the internal combustion engine in the height direction. In the fully-closed state of the rotary valve, the opening 114 is located between a canopy-shaped duct protrusion 113, which is formed on the downstream end surface of an upper wall of the duct 102, and the valve plate 107.
However, in the valve unit shown in FIGS. 17A to 18B, the rotary valve surrounds the duct 102 inserted in the housing 101, and a clearance is formed around the rotary valve.
The clearance around the rotary valve, for example, a clearance formed between the outer surface of the duct 102 and an opposed surface of each of the side plates 106 of the rotary valve is opened to an inner space of the housing 101. Thus, leaked air which has leaked into a top clearance 121 or a side clearance 122 from the clearance around the rotary valve passes through the top clearance 121 or the side clearance 122 to flow into the air flow passage 112.
The above-described application has an object to generate the straight flow (localized flow) that is localized at the upper side of the intake port of the internal combustion engine and the air flow passage 112 in the height direction. However, the clearance is formed around the rotary valve so that an air flow passage for the leaked air is enlarged. Thus, the straight flow (localized flow), which has flowed into the air flow passage 112 from the opening 114 in the fully-closed state of the rotary valve, may be affected by the leaked air which flows into the air flow passage 112 from the top clearance 121 or the side clearance 122, and thereby the straight flow (localized flow) may spread or a flow rate of the localized flow may slow down.
Therefore, in the valve unit shown in FIGS. 17A to 18B, an effect by generation of the localized flow, which is an intended object, cannot be obtained efficiently.